Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w = map(int,input().split())
maze = []
visited = [[0]*(w) for _ in range(h)]
mx = 0
for _ in range(h):
    s = input()
    mx += s.count('.')
    maze.append(list(s))
sy,sx = 0, 0
gy, gx = h-1, w-1
que = deque([(sy,sx,1)])

while que:
    y,x,c = que.popleft()
    if visited[y][x] != 0:
        continue
    visited[y][x] = c
    for dy,dx in zip((1,-1,0,0), (0,0,1,-1)):
        ny,nx = y+dy, x+dx
        if 0<=ny<h and 0<=nx<w:
            if maze[ny][nx]=='.':
                que.append((ny,nx,c+1))

print(mx-visited[gy][gx] if visited[gy][gx]!=0 else -1)